Talk:Honeywell 200

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[edit] Does anybody have the Programmer's Reference Guide

It's been over 30 years since I've worked on a 200 series computer, so some of this may be foggy.

Address mode 2 had no index registers, the entire 12 bits was the operand address giving a 4,096 character address range.

Address mode 3 had a 15 bit address allowing 32,768 bytes to be addressed. The remaining high order 3 bits were the address modifiers. 0 meant no modification and 1-6 meant the address was offset by index registers 1 to 6. Modifier value 7 meant the address was an indirect address, in other words it was the address of a 3 character location in memory which contained the actual address of the operand.

Address mode 4 (this is fuzzy). The address portion was 18 bits and the remaining bits indicated one of 2 sets of 16 index registers or an indirect address.

Change Sequence Mode swapped the instruction register contents with the address contained in the Change Sequence register. This was usually used with instruction trapping mode which caused a sequence swap when an instruction with an item-marked op-code was encountered. Was there an actual CSM instruction, or was trapping the only way to do this?

The system also had a basic interrupt structure and supported basic multi-programming operation. 151.204.233.138 15:37, 11 May 2007 (UTC)